The present invention relates in general to a non-invasive technique for monitoring the temperature of a material or substance that is absorptive at microwave frequencies while being held in a container, connector, bar, or the like that is transparent at microwave frequencies. More particularly, the non-invasive temperature monitor of the invention may be used in association with a microwave sterilizer for providing an accurate reading of the temperature of the material or substance being heated which in the case of microwave sterilization is typically a liquid, such as might be used in continuous ambulatory peritoneal dialysis (CAPD) microwave sterilization. Even more particularly, and in accordance with at least one embodiment of the present invention, there is provided a non-invasive technique for temperature measurement in a microwave sterilization apparatus and in which the liquid being sterilized is held within a connector means to be heated therein by microwave energy for the purpose of sterilization.
Reference is now made herein to copending application Ser. No. 466,894 filed Feb. 17, 1983, now U.S. Pat. No. 4,614,514, on a microwave sterilizer and assigned to the present assignee herein. This sterilizer is described therein as being used for the purpose of sterilizing a coupling or connector that intercouples a conduit from a source of liquid such as a saline solution to a conduit implanted in the body. The apparatus of this sterilizer comprises a guided wave member adapted to enclose the coupling or connector and means for heating by excitation of the guided wave member to heat an initial charge of the liquid to an elevated temperature for a time long enough to destroy bacteria. In this apparatus, it has been assumed that the proper sterilization occurs by virtue of the microwave power having been applied for a specified period of time. The basic problem that has come about is that, because the actual temperature of the liquid or solution is not being measured, one cannot be assured that sufficient sterilization has taken place. For example, if the microwave source is not functioning properly and is say, not putting out the require power, then even though the sterilization occcurs for what appears to be a sufficient period of time, in fact, sufficient sterilization may not have occurred.
The common technique for measuring temperature is to monitor the surface of the container. However, if the container, connector, bar or the like is of insulating or semi-insulating material, it will not be possible to obtain exact temperature measurements. Also, there will tend to be a thermal lag.
Accordingly, it is an object of the present invention to provide a technique for monitoring the temperature, on a non-invasive basis, of a material or substance, usually a liquid, that is absorptive at microwave frequencies (also being heated by microwave energy) while being held in a container, bag, connector, or the like that is transparent at microwave frequencies.
Another object of the present invention is to provide a non-invasive technique for the measurement of temperature of a sterilizing substance which is usually a liquid in association with microwave heating of the liquid for sterilization purposes. In accordance with the invention, this combination of sterilization and temperature detection occurs without any interference whereby the heating applied is at a different frequency than the detection frequency.
Another object of the present invention is to provide a non-invasive temperature monitor that is of relatively simple construction, adapts itself readily to the microwave sterilizer and which can be made in miniature size and in which monitoring can occur quite easily so that the required temperature for sterilization can be readily achieved.
Still another object of the present invention is to provide an improved means for in particular, the warming of the solutions which are absorptive to microwave energy and which are typically contained in plastic bags or the like that are transparent to microwave energy.
A further object of the present invention is to provide a means as set forth in the preceding claim and which is in the form of a conformal array of elements particularly adapted for heating of relatively large solution bags or containers.